Single-phase-motor control.



E. F. W. ALBXANDBRSON. SINGLE PHASE MOTOR common I APPLICATION FILEDOCT. 31, 1907 949,346. Patented Feb. 15, mm

2 SHEETS-43113331 1 W v lrwcmfm W Ernst EW/Uexandermn.

I ay-MM AEG/ E. F, W. ALEXANDERSON. SINGLE PHA$E MOTOR CONTROL.APPLICATION FILED 001*. 31, 1907.

2 SHEETS-SHEET 2,

nyz.

witnesse mvtntor Ernsfi FWAlsxanderson Patented Feb. 15, 1910.

i To all whom it may concern:

. unopposed, it produces at the instant of UNITED sT-A rns PATENTOFFICE.

ERNST Ii. ALEXANDERSON, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NE? YORK.

SINGLE-PHASE-MOTOR CONTROL.

Specification of Letters Patent. Patented Feb. 15, 1910.

Application filed October 31, 1907. Serial No. 400,102.

Be it known that I,- Ennsr F. W. ALEXAN- onason, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful' improvements in Single-.lhasedi'lotorControl, of which the following is a specification.

My invention relates to the coi'itrol of single-phase motors of thecommutator type, and consists in an improvement in the method, t controldescribed in my former application, Serial No. 583,807, filed July 15,1.907.

in my former application l'pointed out the fact that in what is known asthe repulsion motor, in which the armature is shortclrcuited, thereexists an inducing field which for low speeds has a good efi'ect onwnnuutation, since the eleclromotive force imluced in theshort-circuiled coils by cutting this field opposes the electromotiveforce due to the transformer action of the exciting. or cross-field; butthat at high speeds this electromotivc force due to cutting the imlucinglield becomes excessive. I, accordingly, disclosed a control s stem inwhich, for low speeds, the armature is short-- circuited, while athigher speeds an electro motive force is introduced into the armaturecircuit, which reduces the strength of the inducing field, and also theexciting winding is introduced into the armature circuit m order toproduce leakage fields which tend to neutralize the commutationreactance'. My present invention is particularly applicable to a controlsystem of this general character, and has pa rlicular reference to thestarting connections. At the instant of starting, although the inducingfield exists, there is ho electromotive force induced by it in theshortcircuited coils, since the rate of cutting this field is zero. Theelectromotive force induced by the transformer action of the excitingfield is a maximum, and since it starting heavy currents in the armaturecoils short-cn'cuited by the brushes. These heavy currents not only tendto produce sparking at starting, but further react upon the excitingfield which produces them, distorting the phase of this field so that itis no longer in phase with the motor current. suits in reducing thestarting torque of the motor.

This r'c-.

- In an application, Serial No. 392,632, filed by G. H. Hill, September13, 1 907, and assigned to the General Electric Company, a

starting connection for single-phase commutator motors is described, inwhich a definite voltage 1s impressed on the terminals oi the field orexciting winding by placing it in shunt to the other windings. By fixingthe amount and phase of the terminal voltage impressed on the excitingWinding, the

amount and phase of the exciting flux is positively fixed, and althoughthis flux lags nearly ninety degrees behind the impressed voltage, thecurrents in inducing and armature. windings in the case of a repulsionm0- tor, or in the compensating and armature windings in the case of aseries motor, also lag at the moment of starting nearly ninety degreesbehind the impressed voltage, so that the exciting flux at starting issubstantially in phase with the motor current. As soon as the motorstarts, the phase of the motor currents is advanced by thecounter-electromotive force induced by rotation. Therefore, when theconnection described by Mr. Hill is employed at starting, it can be mainlained only momentarily.

My invention in one aspect consists not onlyin fixing the amount andphase of the terminal voltage of the exciting winding at starting, butfurther fixing its phase slightly in advance of the voltage impressedon' the other motor windings. This may conveniently be accomplished byplacing a noninductive resistance in series with the exciting winding,and then connecting the exthe motor currents come more nearly into Iphase with the motor terminal voltage they, are first brought into phasewith the exciting fiux. and then get in advance of it. There results anappreciable range of speed over which the motor currents are nearly inphase with the exciting flux, so that the fixed voltage may bemaintained on the exciting winding until the speed of the motor hasbecome high enough to produce in the armature coil short-circuitcd bythe brushes an appreciable voltage due to cutting the inducipzg field."In other words, the-starting con ctions may be longer maintained, 86

for control in accordance with tron; F igs. 2 to 5 are diagrams of thecirtion ofthe exciting winding is employed at starting.

My invention further comprises inserting in the armature short-circuitat starting a voltage reversed in phase with respect to the voltagewhich is impressed on the armature for high speeds. This reverse voltagestrengthens the inducing field, and consequently assist commutation.

My invention will best be understood by reference to the accompanyingdrawings, in which- Figure 1 shows a pair of motors arranged myinvencuitconnections established by the controlling switch of Fig. 1 inits several positions, only a single motor being shown, to avoidcomplicating the diagrams; and Fig. 6

I shows a modified arrangement of the startin connections.

n Fig. l, A A represent the armatures, B B the exciting windings, and CC the inducing windings of a pair of single-phase motors of thecommutatortype. The windings C C, which act as inducing windings forrepulsion motor operation, would commonly be termed the compensatingwindings in series motor operation, but to avoid unnecessary words, Ishall simply term these windings inducing windings with theunderstanding that the term applies both to repulsion and to compensatedseries motors, and designates the wmding which produces a magneto-motiveforce in line with that of the armature. D represents a transformerwinding, 01; other suitable source of current for the motbrs. Erepresents acontrolling switch, and F a non-inductive resistance.

With the controlling switch F. in its first position, as indicated bythe first dotted line,

connections are established which are shown for a single motor in Fig.2, with the conl trolling switch omitted. The armature A isshort-circulted, while the exciting winding B and inducing winding- Care connected in parallel with the non-inductive resistance F in serieswith the exciting winding. The effectof the non-inductive resistance inthe exciting circuit is to advance the phase of the voltage at theterminals-of the exciting winding with respect to the voltage oftransformer D. Therefore, although the cur' rent in the exciting windingB lags nearly ninety degrees behind its terminal voltage, this currentis in advance of the current of the inducing winding, since atstartingthe current in the inducing winding also lags nearly ninety degreesbehind its terminal voltage. instant of starting is somewhat in advanceof the current in the inducing winding and Therefore, the exciting fluxatthe of the currentin the armature A, which is substantially in phasewith the current in the inducing winding. This phase-displacement,however, is not sufficient materially to reduce the starting torque, andas soon as the armature starts the resulting counterelectromotive forceadvances the phase of the currents in armature and inducing windings, soas to. bring them first into phase with, and then in advance of, theexciting flux. 1f the non-inductive resistance F is properlyproportioned, there is an appreciable range of speed over which theexciting flux and the currents in the other windings .are substantiallyin phase, so that the controlling switch need not be shifted from itsstarting position until the motor has reached an appreciable speed.

In its E establishes the connections shown in Fig. 3, which are theordinary repulsion motor connections with the armature A short-circuitedand with'the exciting and inducing windings in series, so that thecurrent in the exciting winding is in phase with the currents in theother windings. This connection may be employed for acceleration orlowspeed operation, and is the same connection which in my earlierapplicatiornnbove referred to, was employed both for starting and forlowspeed operation or acceleration.

iVhen the controlling switch E, of Fig. 1, is moved to its thirdposition, the connec tions shown. in.Fig. l are established. In thisfigure the exciting winding B is included in the armature circuit, and asmall voltage is also included in this circuit. As explained in myearlier application, the purpose of including the exciting winding inthe armature circuit is to introduce leakage fields into the motor,which assist in neutralizing commutation reactance, while the purpose ofthe voltage introduced into the armature circuit is to reduce theinducing tlux, which becomes excessive at high speeds.

In passing from its third to its fourth position, switch E simplyincreases the voltage innaressed on the armature circuit, as shown inFig. i), so that the inducing field is further weakened. The connectionsof Figs. 3, 4i and 5 are the same as the connections disclosed in myearlier application.

While the effect on commutation of the inducing field becomes excessiveabove synchronism, if the armature is left shortsecond positioncontrolling switch circuitcd, at low speeds it is too weak, when thearmature is short-circuited, as in Fig. 2, to neutralize theclcctromotive forces due to .the transformer action'of the excitingfield. Just as the inducing field may be weakened by inserting in thearmature circuit a voltage of a certain phase, so also it may bestrengthened by a voltage of the opposite phase. Such an arrangementis'shown in ,Fig. 6, which is the same as Fig. 2, except that thearmature, instead of being directly short-circuited, has impressed on ita voltage of opposite phase with respect to the voltage which isincluded in the armature circuit for highspeed operation. The effect ofthe connection shown in Fig. 6 is to increase the strength of theinducing field and to improve braking at high speeds, it will generallybe advisable to arrange the controller to skip the starting connectionson returning from full speed to oil position. This arrangement may hebrought about several ways, as, for nstance, by the contact constructionshown in PatentNo. 798,375, issued to H. E. lVhite, Au ust 29, 1905.

\' hat I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. Thc'method of operating a single-phase motor of the commutator type,whichconsists in impressing on the terminals ofthe exciting winding atstarting a voltage fixed in amount and phase anti in advance of theterminal voltageof.tl1e' otlier windings, and

as soon as the-motor, has'started supplying to the exciting winding :1current- 111 phase with the currents. of the ot)rcr motor windlu s.

h :2. The method of operating a single-phase motor of the commutatortype, winch consists in connecting a non-inductive resistance i .inseries withthe exciting winding at starting and impressing a shuntvoltage on the exciting circuit, and as soon as ,the motor has startedconnecting the exciting winding in series with the other motor windings.

3. The method of'star'ting a single-phase motor of thecommutator typehaving inducing and exciting windings on the stator, which consists inconnectingthe armature in a locaL closed circuit and connecting theinducing and exciting windings in shunt to each other with anon-inductive resistance in series with the exciting winding,

4. The method ofoperating a single-phase motor of the commutator typehaving inducing and exciting windings on the stator, which consists atstarting in connecting the armature in a localclosed circuit and the' inducing and exciting windings in shunt to each other, and as soon as themotor has started connecting the exciting windings in series with one ofthe other windings.

5. The method of operating a single-phase motor of the commutator typehaving inducing and exciting windii'igs' on the stator,

which consists at starting in connecting thearmature in a local closecircuit and the inducing and exciting windings 1n shunt. to each otherwith a non-inductive resistance in series with the exciting winding, andas soon as the motor has started connectin the exciting winding inseries with. one o? the other windings.

v 6. The method of starting a single-phase motor of the commutator typehaving inducing and exciting windings on the stator, which consists inconnecting the armature in a local closed circuit with a source ofvoltage and connecting the inducing and exciting windings iii-shunt toeach other with a noninductive resistance in serieswvith the citingwinding. I

7. The method of operating a single-phase motor of the commutator typehaving inducingand exciting Willtlll'lgS on the'stator, which consistsat starting in connecting the armature in a local closed circuit with asource of voltage and connecting the inducing and exciting windings inshunt to each other, and as soon as the motor has started connecting theexciting, winding in series with one of the other windings.

8. The method of operatmga single-phase motor of the con'n'nutator typehaving in ducing and exciting windings on the stator,

which'consists at startingin eonuecting the armature in a local closedcircuit with a source of voltage and connecting the inducmg and excitingwindings in shunt to each other with a non-inductive resistance inseries with the exciting winding, and as soon as the motor has startedconnecting the exciting winding in a series with one. oi? the otherwindings.

9. 'lhemethod of operating a single-phase motor of the commutator typehaving inducing and exciting windings on the stator,

which consists in connecting the arn'niture in a local closed circ iitand connecting the inducing and excitingwmdmgs 1'11 shunt tor starting,connecting the inducing and exciting windings in series foraccelerating, and connecting the exciting winding in a local closedcircuit with the armature and with a source of voltage for running.

10. The method of operating a singlephase motor of the commutator typehaving inducing and exciting windings on the stator, which consists inconnecting the armature in a local closed circuit and connecting theinducing and exciting windings in shout to each other with anon-inductive resistance in series with the exciting winding forstarting, connecting the inchicing and exciting windings in series foraccclenting, and connecting the exciting winding in' a local closedcircuit with the armature. and with a source of voltage for running.

11. The method of operating a singlephase motor of the commutator typehaving inducing and exciting windings on stator which consists inconnecting the armature in a local closed circuit with a source ofvoltage at starting, and for running including the exciting winding inthe the starting,

exciting windings ductive resistance,

the exciting ductive resistance,

"i -ii reversing the phase of 5 therefor, a non-inductive resistance,and a arranged to,connect said controlling switch resistance in serieswith the exciting winding and to connect. the exciting circuit to thesource in shunt to the main motor circuit at and in a subsequentposition to connect the exciting winding in series with the other motorwindings.

13. In combination, a single-phase motor ot' .the commutator type havinginducing and 15 exciting windings on the stator, and a controllingswitch arranged in its starting position to connect the motor armaturein a local closed circuit and to connect the inducing and excitingwindings in shunt to each other,

20 and in a subsequentposition to connect the exciting winding in serieswith one ofthe other motor windings.

14. In combination,a single-phase motor of the commutator on the statora non-in ductive resistance, and a controlling switch arranged in itsstarting position to connect the motor armature in a local closedcircuit and to connect the exciting ducing winding.

15. In combination, a singlephase motor of the commutator type havinginducing and exciting windings on the stator, a non-in and a controllingswitch arranged in its starting position to connect the exciting windingin series with the resistance and in shunt to the inducing winding, andin a subsequent position to connect winding in series with one of theother motor windings.

16 In combination, a single-phase motor of the commutator type havinginducing and exciting windings on the stator, a non-i1 typehavinginducing and winding in series 3.0 with the resistance and 1nshunt. to the inand means for establishl ing a local closed circuit forthe armat-ure to the inducing winding at starting.

17. In combination, a single-phase motor exciting windings on thestator, and acontrolling switch arranged in its first position toconnect the armature in a local closed circuit and to connect theinducing and exciting windings in parallel, in a subsequent po sition toconnect the inducing and exciting windings in series, and in a stillsubsequent position to include the exciting Winding in the armaturecircuit and to impress a vol tage thereon.

18. In combination, a single-phase motor of the commutator type havinginducing and exciting windings on thestator a non-inductive resistance,and a controllingswitch arranged in its first position to connect thearmature in a local closed circuit and to connect the exciting windingin series with the resistance and in shunt to the inducing winding, in asubsequent position to connect the inducing and exciting windings inseries, and in a still subsequent position to include the excitingwinding in the armature circuit and to impress a voltage thereon.

19. In combination, a single-phase motor of the commutator type havinginducing and exciting windings on the stator, and means armature andimpressing a voltage on the armature terminals at starting and forincluding the exciting winding in said circuit and reversing the phaseof said voltage for I running.

In witness whereof, I have hereunto set my hand this 29th day ofOctober, 1907.

ERNST F. W. ALEXANDERSON.

Witnesses:

BENJAMIN B. HULL, HELEN Onronp.

of the commutator type having inducing'and y for establishing a localclosed circuit for the and impressing a voltage on the armature

